"Slow Reacting Substance of Anaphylaxis" (SRS-A) has been shown to be a highly potent bronchoconstricting substance which is released primarily from mast cells and basophils on antigenic challenge. SRS-A has been proposed as a primary mediator in human asthma. SRS-A, in addition to its pronounced effects on lung tissue, also produces permeability changes in skin and may be involved in acute cutaneous allergic reactions. Further, SRS-A has been shown to effect depression of ventricular contraction and potentiation of the cardiovascular effects of histamine.
The discovery of the naturally occurring leukotrienes and their relationship to SRS-A has reinforced interest in SRS-A and other arachidonate metabolites. SRS-A derived from mouse, rat, guinea pig and man have all been characterized as mixtures of leukotriene-C.sub.4 (LTC.sub.4), leukotriene-D.sub.4 (LTD.sub.4) and leukotriene-E.sub.4 (LTE.sub.4), the structural formulae of which are represented below. ##STR1##
Leukotrienes are a group of eicosanoids formed from arachidonic acid metabolism via the lipoxygenase pathway. These lipid derivatives originate from LTA.sub.4 and are of two types: (1) those containing a sulfido-peptide side chain (LTC.sub.4, LTD.sub.4, and LTE.sub.4), and (2) those that are nonpeptidic (LTB.sub.4). Leukotrienes comprise a group of naturally occurring substances that have the potential to contribute significantly to the pathogenesis of a variety of inflammatory and ischemic disorders. The pathophysiological role of leukotrienes has been the focus of recent intensive studies.
As summarized by Lefer, A. M., Biochemical Pharmacology, 35, 2, 123-127 (1986), both the peptide and non-peptide leukotrienes exert microcirculatory actions, promoting leakage of fluid across the capillary endothelial membrane in most types of vascular beds. LTB.sub.4 has potent chemotactic actions and contributes to the recruitment and adherence of mobile scavenger cells to the endothelial membrane. LTC.sub.4, LTD.sub.4 and LTE.sub.4 stimulate a variety of types of muscles. LTC.sub.4 and LTD.sub.4 are potent bronchoconstrictors and effective stimulators of vascular smooth muscle. This vasoconstrictor effect has been shown to occur in pulmonary, coronary, cerebral, renal, and mesenteric vasculatures.
Leukotrienes have been implicated in a number of pulmonary diseases. Leukotrienes are known to be potent bronchoconstrictors in humans. LTC.sub.4 and LTD.sub.4 have been shown to be potent and selective peripheral airway agonists, being more active than histamine. [See Drazen, J. M. et al., Proc. Nat'l. Acad. Sci. USA, 77, 7, 4354-4358 (1980)]. LTC.sub.4 and LTD.sub.4 have been shown to increase the release of mucus from human airways in vitro. [See Marom, Z. et al., Am. Rev. Respir. Dis., 126, 449-451 (1982)]. The leukotriene antagonists of the present invention can be useful in the treatment of allergic or non-allergic bronchial asthma or pulmonary anaphylaxis.
The presence of leukotrienes in the sputum of patients having cystic fibrosis, chronic bronchitis, and bronchiectasis at levels likely to have pathophysiological effects has been demonstrated by Zakrzewski et al. [See Zakrzewski, J. T. et al., Prostaglandins, 28, 5, 641 (1984).] Treatment of these diseases constitutes additional possible utility for leukotriene antagonists.
Leukotrienes have been identified in the nasal secretions of allergic subjects who underwent in vivo challenge with specific antigen. The release of the leukotrienes was correlated with typical allergic signs and symptoms. [See Creticos, P. S. et al., New England J. of Med., 310, 25, 1626-1629 (1984).] This suggests that allergic rhinitis is another area of utility for leukotriene antagonists.
The role of leukotrienes and the specificity and selectivity of a particular leukotriene antagonist in an animal model of the adult respiratory distress syndrome was investigated by Snapper et al. [See Snapper, J. R. et al., Abstracts of Int'l Conf. on Prostaglandins and Related Comp., Florence, Italy, p. 495 (June 1986.)] Elevated concentrations of LTD.sub.4 were shown in pulmonary edema fluid of patients with adult respiratory distress syndrome. [See Matthay, M. et al., J. Clin. Immunol., 4, 479-483 (1984).] Markedly elevated leukotriene levels have been shown in the edema fluid of a patient with pulmonary edema after cardiopulmonary bypass. [See Swerdlow, B. N., et al., Anesth. Analg., 65, 306-308, (1986).] LTC and LTD have also been shown to have a direct systemic arterial hypotensive effect and produce vasoconstriction and increased vasopermeability. [See Drazen et al., ibid.] This suggests leukotriene antagonists can also be useful in the areas of adult respiratory distress syndrome, pulmonary edema, and hypertension.
Leukotrienes have also been directory or indirectly implicated in a variety of non-pulmonary diseases in the ocular, dermatologic, cardiovascular, renal, trauma, inflammatory, carcinogenic and other areas.
Further evidence of leukotrienes as mediators of allergic reactions is provided by the identification of leukotrienes in tear fluids from subjects following a conjunctival provocation test and in skin blister fluids after allergen challenge in allergic skin diseases and conjunctival mucosa. [See Bisgaard, H. et al., Allergy, 40, 417-423 (1985).] Leukotriene immunoreactivity has also been shown to be present in the aqueous humor of human patients with and without uveitis. The concentrations of leukotrienes were sufficiently high that these mediators were expected to contribute in a meaningful way to tissue responses. [See Parker, J. A. et al., Arch Ophthalmol, 104, 722-724 (1986).] It has also been demonstrated that psoriatic skin has elevated levels of leukotrienes. [See Ford-Hutchinson, J. Allergy Clin. Immunol., 74, 437-440 (1984).] Local effects of intracutaneous injections of synthetic leukotrienes in human skin were demonstrated by Soter et al. [(See Soter et al., J. Clin. Invest Dermatol, 80, 115-119 (1983).] Cutaneous vasodilation with edema formation and a neutrophil infiltrate were induced. Leukotriene synthesis inhibitors or leukotriene antagonists can also be useful in the treatment of ocular or dermatological diseases such as allergic conjunctivitis, uveitis, allergic dermatitis or psoriasis.
Another area of utility for leukotriene antagonists is in the treatment of cardiovascular diseases. Since peptide leukotrienes are potent coronary vasoconstrictors, they are implicated in a variety of cardiac disorders including arrhythmias, conduction blocks and cardiac depression. Synthetic leukotrienes have been shown to be powerful myocardial depressants, their effects consisting of a decrease in contractile force and coronary flow. The cardiac effects of LTC.sub.4 and LTD.sub.4 have been shown to be antagonized by a specific leukotriene antagonist, thus suggesting usefulness of leukotriene antagonists in the areas of myocardial depression and cardiac anaphylaxis. [See Burke, J. A. et al., J. Pharmacology and Experimental Therapeutics, 221, 1, 235-241 (1982).]
LTC.sub.4 and LTD.sub.4 have been measured in the body fluids of rats in endotoxic shock, but are rapidly cleared from the blood into the bile. Thus leukotrienes are formed in ischemia and shock. Specific inhibitors of leukotriene biosynthesis reduce the level of leukotrienes and therefore reduce manifestations of traumatic shock, endotoxic shock, and acute myocardial ischemia. Leukotriene receptor antagonists have also been shown to reduce manifestations of endotoxic shock and to reduce extension of infarct size. Administration of peptide leukotrienes has been shown to produce significant ischemia or shock. [See Lefer, A. M., Biochemical Pharmacology, 35, 2, 123-127 (1986).] Thus further areas of utility for leukotriene antagonists can be the treatment of myocardial ischemia, acute myocardial infarction, salvage of ischemic myocardium, angina, cardiac arrhythmias, shock and atherosclerosis.
Leukotriene antagonists can also be useful in the area of renal ischemia or renal failure. Bard et al. have shown that LTC.sub.4 produces significant elevation of mean arterial pressure and reductions in cardiac output and renal blood flow, and that such effects can be abolished by a specific leukotriene antagonist. [See Badr, K. F. et al., Circulation Research, 54, 5, 492-499 (1984).] Leukotrienes have also been shown to have a role in endotoxin-induced renal failure and the effects of the leukotrienes selectively antagonized in this model of renal injury. [See Badr, K. F. et al., Kidney International, 30, 474-480 (1986).] LTD.sub.4 has been shown to produce local glomerular constrictor actions which are prevented by treatment with a leukotriene antagonist. [See Badr, K. F. et al., Kidney International, 29, 1, 328 (1986).] LTC.sub.4 has been demonstrated to contract rat glomerular mesangial cells in culture and thereby effect intraglomerular actions to reduce filtration surface area. [See Dunn, M. J. et al., Kidney International, 27, 1, 256 (1985).] Thus another area of utility for leukotriene antagonists can be in the treatment of glomerulonephritis.
Leukotrienes have also been indicated in the area of transplant rejection. An increase in cardiac and renal allograft survival in the presence of a leukotriene receptor antagonist was documented by Foegh et al. [See Foegh, M. L. et al. Advances in Prostaglandin, Thromboxane, and Leukotriene Research, 13, 209-217 (1985).] Rejection of rat renal allografts was shown to produce increased amounts of LTC.sub.4. [See Coffman, T. M. et al., Kidney International, 29, 1, 332 (1986).]
A further area of utility for leukotriene antagonists can be in treatment of tissue trauma, burns, or fractures. A significant increase in the production of cysteinyl leukotrienes was shown after mechanical or thermal trauma sufficient to induce tissue edema and circulatory and respiratory dysfunction. [See Denzlinger, C. et al., Science, 230, 330-332 (1985).]
Leukotrienes have also been shown to have a role in acute inflammatory actions. LTC.sub.4 and LTD.sub.4 have potent effects on vascular caliber and permeability and LTB.sub.4 increases leukocyte adhesion to the endothelium. The arteriolar constriction, plasma leakage, and leukocyte adhesion bear close resemblance to the early events in acute inflammatory reactions. [See Dahlen, S. E. et al., Proc. Natl. Acad. Sci. USA, 78, 6, 3887-3891 (1981).] Mediation of local homeostasis and inflammation by leukotrienes and other mast cell-dependent compounds was also investigated by Lewis et al. [See Lewis, R. A. et al., Nature, 293, 103-108 (1981).] Leukotriene antagonists can therefore be useful in the treatment of inflammatory diseases including rheumatoid arthritis and gout.
Cysteinyl leukotrienes have also been shown to undergo enterohepatic circulation, and thus are indicated in the area of inflammatory liver disease. [See Denzlinger, C. et al., Prostaglandins Leukotrienes and Medicine, 21, 321-322 (1986).] Leukotrienes can also be important mediators of inflammation in inflammatory bowel disease. [See Peskar, B. M. et al., Agents and Actions, 18, 381-383 (1986).] Leukotriene antagonists thus can be useful in the treatment of inflammatory liver and bowel disease.
Leukotrienes have been shown to modulate IL-1 production by human monocytes. [See Rola-Pleszczynski, M. et al., J. immun., 135, 6, 3958-3961 (1985).] This suggests that leukotriene antagonists may play a role in IL-1 medicated functions of monocytes in inflammation and immune reactions.
LTA.sub.4 has been shown to be a factor in inducing carcinogenic tumors and is considered a link between acute immunologic defense reactions and carcinogenesis. Leukotriene antagonists can therefore possibly have utility in treatment of some types of carcinogenic tumors. [See Wischnewsky, G. G. et al. Anticancer Res. 5, 6, 639 (1985).]
Leukotrienes have been implicated in gastric cytodestruction and gastric ulcers. Damage of gastrointestinal mucosa because of potent vasoconstriction and stasis of blood flow is correlated with increased levels of LTC.sub.4. Functional antagonism of leukotriene effects may represent an alternative in treatment of mucosal injury. [See Dreyling, K. W. et al., British J. Pharmacology, 88, 236P (1986), and Peskar, B. M. et al Prostaglandins, 31, 2, 283-193 (1986).] A leukotriene antagonist has been shown to protect against stress-induced gastric ulcers in rats. [See Ogle, C. W. et al., IRCS Med. Sci., 14, 114 (1986).]
Other areas in which leukotriene antagonists can have utility because leukotrienes are indicated as mediators include prevention of premature labor [See Clayton, J. K. et al., Proceedings of the BPS, 573P, 17-19 Dec. 1984]; treatment of migraine headaches [See Gassaniga, P. P. et al., Abstracts Int'l Conf. on Prostaglandins and Related Comp., 121, Florence, Italy (June 1986)]; and treatment of gallstones [See Doty, J. E. et al., Amer. J. of Surgery, 145, 54-61 (1983) and Marom, Z. et al., Amer. Rev. Respir. Dis., 126, 449-451 (1982).]
By antagonizing the effects of LTC.sub.4, LTD.sub.4 and LTE.sub.4 or other pharmacologically active mediators at the end organ, for example, airway smooth muscle, the compounds and pharmaceutical compositions of the instant invention are valuable in the treatment of diseases in subjects, including human or animals, in which leukotrienes are a key factor.